Change Video Speed Online
Slow a clip down or speed it up from 0.25× to 4×. Preview the timing, keep synchronized audio when available, and process everything on your device.
Why change video speed in your browser?
- Includes useful 0.5×, 0.75×, 1.25×, 1.5×, and 2× presets
- Supports custom speeds from 0.25× through 4× with clear validation
- Shows the source and expected output durations before processing starts
- Adjusts video timestamps and audio tempo together to stay synchronized
- Exports even-dimension H.264 and yuv420p MP4 with optional AAC audio
- Runs locally in your browser without an upload, account, or watermark
Frequently asked questions
How does the tool keep audio synchronized?
Video presentation timestamps are divided by the selected speed, while audio uses FFmpeg’s tempo filter. Very slow or fast custom values use a safe chain of tempo filters so the audio duration follows the video.
Does changing audio speed also change pitch?
The audio tempo filter is designed to change timing without the simple chipmunk or deep-voice pitch shift caused by resampling. Extreme settings can still produce audible artifacts, especially with music.
Why does the output duration change?
Output duration equals source duration divided by speed. A 10-second clip at 2× becomes about 5 seconds, while the same clip at 0.5× becomes about 20 seconds. Frame and audio packet boundaries can add a small rounding difference.
What custom speed range is supported?
The safe range is 0.25× through 4×. Values below 1 slow the video; values above 1 speed it up. Extremely slow or fast playback takes more processing and can look or sound less natural.
Can I change speed and remove the audio?
Yes. Turn off “Keep adjusted audio” to create a silent MP4. When audio is enabled, the first available audio track is adjusted and converted to 128 kbps AAC.
Is the operation lossless or uploaded?
No to both. The selected timing requires lossy H.264 re-encoding, but the source file is processed locally in your browser. Subtitles, chapters, location data, and other metadata are not copied.
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